I propose to study properties of taste cells particularly as they relate to epithelial cell characteristics. Specifically, this involves a study of transepithelial ion transport and intercellular connections in taste buds and the relationship of these parameters to chemosensory transduction mechanisms. To provide a focus for the study, two hypotheses will be tested: (1) Chemosensory transduction mechanisms in taste cells are intimately linked to transepithelial ionic transport and intercellular (GAP) junctions; (2) There is an ongoing release of neurotransmitter from taste cells and this ongoing release is modulated by chemosensory stimulation. The study will be conducted primarily on mudpuppies, Necturus maculosus. Other species (mouse, hamster, rat) will be used as supplementary material as described in Methods. The experiments will consist of electrophysiological recordings, light microscopy and ultrastructural investigations. Lingual tissue will be mounted in a micro-Ussing chamber to allow us to impale single taste cells while controlling transepithelial ionic transport and while exchanging mucosal and serosal bathing solutions independently. We will measure the biophysical properties of apical and basolateral membranes from taste cells and how (whether) transepithelial Na transport is linked to taste transduction. We will also investigate the presence of Na pumps in taste cells with histochemical and immunocytochemical techniques. Putative synaptic transmitters will be identified by immunocytochemical methodology in taste cells. Gap junctions between taste cells will be explored with Lucifer yellow dye injections and ultrastructural techniques. This data will provide an essential link between studies on single channel conductances on isolated taste cells and whole animal studies. The information will bear upon how taste cells function in situ in the intact lingual epithelium under physiological conditions.